Background & Management
Definition
Displacement of proximal femoral epiphysis in the immature hip
- due to imbalance of mechanical and endocrine factors
Epidemiology
M 12-14
F 11-13
3 / 100 000
- male predominance
- L > R
High in Polynesians and African - Americans
- 7% risk to second family member
Bilateral SUFE
No endocrine abnormality
- 20% at time of of diagnosis
- another 20% during diagnosis
- up to 60% with long term follow up
Endocrine abnormality
- up to 75%
Aetiology
Predisposing factors
- obesity / height
- rapid growth
- endocrinopathies
1. Mechanical
A. Weight / Height
- 50% over 95th percentile weight
- 50% over 97th percentile height
B. Growth plate
- widened zone of hypertrophy
- increased slope
- increased retroversion Southwick angle > 14o
- assess other side
- if very retroverted is indication to prophylactic pinning
2. Endocrine
Imbalance of
- Testosterone - causes physeal fusion
- Growth hormone - causes physeal hypertrophy / weakens
Causes
- hypothyroidism
- renal rickets
- hypopituitary
- acromegaly
- CRF
3. Other
Marfan's / Downs / Klinefelter's
Chemo therapy / DXRT
GH
Pathology
Widened hypertrophic zone
- constitutes 60% of physeal width
Abnormality of Hypertrophic & Proliferative Zones
- failure occurs in this zone at junction with proliferative zone
- disordered chondrocyte columns
- decreased number of cells
- cells smaller
- increased number of dead and degenerative cells
Head remains in acetabulum via L. Teres
- neck displaces anterosuperior on physis and ER
- head slips posterior / inferior on neck
Classification
Chronological
Acute < 3/52 symptoms
Acute on Chronic
Chronic >3/52
Morphological
Southwick Slip angle
- lateral X-ray / frogs legs
- epiphyseal-shaft angle
- abnormal angle minus normal angle
- <30° / 30- 50 / >50°
- mild / moderate / severe
Stability
Loder JBJS 1993
Stable
- able to able to weight / 0% AVN
Unstable
- unable to weight bear / 50% AVN
History
Overweight adolescent boy hip or knee pain
Examination
Limps
Walk with ER (chronic)
Flexes into Abduction / ER
Limitation IR / Abduction
LLD (real and apparent)
X-ray
AP
Trethowan Line / Kleins Line
- line along superior neck usually transects 20% head
Widened physis
Inferomedial remodelling in chronic slip
Frog Leg Laterals / Shoot through lateral
Shoot through lateral
- best to avoid frog leg lateral as may displace slip
Posteriorly displaced & angulated
Measure Southwick Angle
- calculate severity of slip
- also estimates risk of slip of other side / looking for retroversion
Management
Aims
1. Prevent further slip / obtain physis fusion
- 30% will continue untreated
2 Prevent deformity and OA
- MUA / ORIF / osteotomy
3. Avoid complications
Algorithm
Dr Deborah Eastwood
APOS 2008
Greater Ormond St, London
1. True acute / unstable
- < 24 hours
- treat like fracture
- "inadvertent" correction
2. Pin in situ
3. Severe slip / unable to pin in situ
- refer tertiary pediatric hospital
- wait 3/52, traction
- intracapsular ostetomy
4. Moderate - severe deformity post fusion
- refer for osteotomy
In Situ Pinning
Gold Standard
- supine on bed / traction table
- avoid reduction / allowed some minor, non forceful internal rotation
- entry on anterior femoral neck to get into posteriorly displaced physis
- central placement in head crossing physis
- 5 threads crossing physis
- single screw in central location with satisfactory fixation avoiding joint penetration
- approach & withdrawal X-ray to ensure no joint penetration
- +/- pin other side
CT post operatively
- ensure no screw protrusion
TWB 6/52
Serial Xray
- ensure epiphysis doesn't grow off screw
- screw can break / can lose position
- observe til physis closes
- no indication to remove pin
Results
Weinstein et al JBJS Am 1991
- 40 year follow up of 155 hips
- some pinned in situ / some realigned / some reduced
- rates of OA / AVN / chondrolysis increased with severity of slip
- rates of OA / AVN / chondrolysis increased with reduction / realigned
- regardless of severity of slip, pinning in situ had best results with lowest complications
Closed Reduction Prior to Pinning
Disadvantage
Traditionally associated with higher risk AVN
Advantage
Theorectical
- may decrease AVN in severe, unstable hips
- prevent severe deformity / late OA
Indication
Acute & unstable < 24 hours
Results
Peterson et al J Paediatr Orthop 1997
- 91 cases of severe, acute, unstable slips
- 42 closed reduction < 24hrs AVN 7%
- 49 closed reduction > 24hrs AVN 20%
- hypothesised that had acute obstruction of epiphyseal vessels
- timely decompression allows revascularisation
- treat an acute unstable slip as per a fracture
- these have up to 50% AVN rate anyway
- emergency operation
Chen et al J Paediatr Orthop 2009
- 30 acute, unstable slips
- 25 closed reductions and 5 open reductions with release hematoma
- 4 cases of AVN
Open Reduction Prior to Pinning
Indications
- severely displaced slips
Reasoning
- moderate or severe slips do poorly in long term
- best treatment is intra-capsular reduction or osteotomy
- risk AVN either way
- acute open reduction easier
- also decompress hip
Technique Subcapital Osteotomy
- trochanteric slide osteotomy / Ganz Osteotomy / digastric osteotomy
- anterior capsulotomy
- Z shaped to preserve superior vessel along neck) along anterior acetabulum and inferior neck
- capsule banana skinned off neck
- epiphysis taken off neck, still attached to capsule
- neck debrided to avoid tensioning of posterior vessels
- head replaced and pinned as per normal
Results
Slongo and Ganz et al Oper Orthop Traumatol 2007
- 30 cases of acute slip treated with subcapital osteotomy
- no cases of AVN
Prophylactic Pinning
Issues
Can justify but may cause complications
- i.e. chondrolysis, subtrochanteric fracture secondary to screw
Incidence bilateral slips
- unknown
- may be > 35%
- high incidence of asymptomatic and mild contralateral slips
Major indications
- young
- unreliable
- geographic isolation
- endocrine
Technique of Pin in Situ
Set up
1. Supine on radiolucent table
- very easy to set up
- much faster if pinning both sides / reduced set up
- theoretical risk of displacing slip / inadvertant manipulation
- lateral by flexing and full ER of hip / frog legs
2. Traction Table
- easy to get AP and lateral
- need 2 set ups for bilateral pinning
- takes longer in this regard
Technique
Draw anterior and lateral lines
- get AP, draw line mark using radiopague ruler to centre of head
- get lateral, repeat
- intersection of points is incision site
Stab incision
- guide wire percutaneously to neck
- more anterior entry point on femoral neck required the more the epiphysis is displaced posteriorly
- central in head on both views
- ensure don't penetrate head
- cannulated drill
- 7 mm screw
- 8-10 mm or 4-5 threads across physis
- do far and away screening / approach withdraw
- this ensures screw is not in joint